Joe Jeep

Bump. No one plugs their MJ in overnight?

So, does what does the O2 sensor do exactly and if it is not functioning what happens to the MJ? Is it a part that wears out or is there a way to test if it is functioning? On the 2.5, this sensor is located on the exhaust manifold, right?

What's the $ for a new O2 sensor?

Sorry about that. :oops: A tank heater for the coolant to keep the engine warm overnight when the temps are below 0*F. I know that there are several types of heater as well: the frost plug, lower radiator hose, and magnetic heaters as well. I have a tank heater, meaning that the coolant enters an external tank with a heating element then as it warms it starts to circulate hot coolant around the engine block. Or atleast this is my understanding. Here is an example of what I am talking about.

I got a new tank heater for free for the ol' MJ. It did not come with instructions but I think I know how to hook it up. Anyone have one on their MJ? Any pictures? I am going to connect it to the heater line but I am not sure where I am going to connect it to the block for circulation? Anyone? Thanks.

I was just wondering how well the 2.5 ECU and TBI are at adapting to changning conditions. I was poking around the engine this weekend and noticed that a few of the vacuum lines are in need of replacing. They are not broken, but cracked. When I start the truck, it runs a bit rough for the first ~15-30 seconds and then settles out. It has 235000 miles so it isn't new (though the PO had the topend done at ~115000 miles). I am sure the O2 sensor is original as well as many of the hoses which I am thinking about replacing. This is my first vehicle with TBI injection so just wondering more about how it works. Thanks.

What controls the shift light arrow on the dash? Stict rpm or...? On my way to work this morning I noticed the shift arrow aluminating when I was around 2000rpm. The lighted arrow on the dash was telling me to put the truck into 4th at around 30mph (~2000rpm) which seems really low for a truck only having 4 speeds. For reference, the truck idles around ~700 to 800rpms when warm on an aftermarket tach I installed. The reason I am wondering is because I suspect the truck runs rich, but I drive it so infrequently I don't know the average mileage (in the last 5 months I have driven it 495miles). The only time the truck went on a trip, it was pulling a empty trailer and got 20mpg and loaded with ~900lbs on the way back it got 17mpg.

I put an aftermarket tach on my '87 2.5L and connected the signal line from the tach to the tach line in the wiring harness. I think it was under the black cover on the passenger side of the engine compartment.

I had this problem on my MJ. With the lights on, the left side turn signal would be on. If I used the turn signal, it would flash. If I used the hazards, the front turn signals would flash but not at the same time (like a cop car). It turned out to be a bad ground in the wiring. On mine, it was located in the loom that runs right behind the grill. I traced the wires and found the bad ground and fixed it. Hasn't happened now for 3 years. Good luck!

Thanks for the reply, now I know what is going on under the truck. My explanation was not the best because I didn't fully understand what was going on for the rear brakes. This is my first Jeep and my first vehicle that needed brake work beyond bleeding and replacing pads (it's hard to believe and I have owned some real turds). I agree with you, keep it simple if you can. That is why I was confused for so long about the lines on the truck. I have lots of experience on motorcycles: master cylinder => brake line => caliper. Simple. Also, last night I was able to replace the brake line and bleed all of the brakes. No leaks and the brakes are better then before the line blew up. Thanks to everyone for the help. :cheers:

77% Optimus Prime 8)

Well, I finally got around to my brakes again last night. I was able to free up all of the rusted connections using a locking pliers. :brows: Not a proper wrench, but not a sawzall either. Tonight I will be able to hook up my line and bleed the brakes finally. :D While I was under the MJ, I traced the brake line around and had a couple of questions about the function of the junction boxes and such. I haven't had to work on this aspect of the truck to date so this is new to me. So, here's my take on what's going on under the bed. There are two brake lines from the master cylinder that run to the rear of the truck. One line goes to a junction box that is connected to the proportioning valve that operates off the axle (this is the line that ruptured). This box has a hard line that goes to another junction box by the bed rail that the other brake line from the master cylinder goes to. One line leaves this box and connects to the rubber line which is connected to a junction box on the rear axle (below the proportioning valve). Out of this box, a line heads to each wheel cylinder. Am I getting this right? Why two brakes lines heading to one line then to each wheel cylinder? Is this incase one line ruptures you still have some rear brakes? Also, where does the rubber line from the axle go to (I couldn't see where it terminates) and what does it do? Last question for now, when people swap axles what changes do you make to the brake system?

So, I bought the brakeline and such to fix my blow out on the rear of my Comanche. When I started to check to see how much rusty line to remove, I found that the leak was where the coil over the brake line is. The rear brake line in questions leads to the block on the axle (for the driver's side rear brake). Well, I can't get the coil off the brake line, I can't remove the fitting from the block and even if I could, I can't turn the bleeder on the drum. Everything is rusted solid. So, not being able to do anything else, I just looked around the underside of the truck. Rust is everywhere, it basically starts from the bed to the bumper in back. I have everything soaking in penetrating oil right now with a hope that it will be able to fix it using wrenches...but ahhhhhhhh rust! :headpop: Yes, I own a maul and a sawzall...

What is involved in switching from manual to power steering. I know the pump and belt, but it sounds like the box as well. :roll:

Thanks for the help with the brakes; I picked up my needed equipment last night for replacing the line. I am going to give it a go tonight so it is wait and see... My MJ has manual steering and there is a fair amount of play in the steering wheel. I know with this type of steering, it is not ever going to feel tight (and shouldn't) but looking at the box, there is a possibility for adjustment. My manual (Haynes; hey it was free, just like the truck) doesn't cover how to adjust this. Is this worth it? Also, it says that fluid in the box is gear lube. Is this worth replacing? There is more play in the wheel to the right than left. I had a friend turn the steering wheel and all of the play appears to be in the box. So, what's the thought on this? Adjust? Change lube? Switch to power steering?

Thanks for the additional info and pictures. The rear height sensing valve is there and intact so I will probably leave it alone for now unless further investigation leads me to remove it. The brake lines are solid until the gas tank area and then there is rust on the lines to the first union. I will probably try to splice into the solid line, replacing the line from around the fuel filter until the union. I won't be getting to this for a few days, so if anyone else has something to share, please do. Also, I am located in River Falls which is on the WI/MN border.

Could you explain in more detail the elimination of the proportioning valve? When I was under the truck, there was a whole lotta brake line running everywhere. The leak is right behind the gas tank, close the first union right by the bed rail before it drops down to the axle (to another union, if memory serves me correctly). If I could make it simpler back there, I would be interested.

Hello all, I am glad to have found this forum. I have a '87 Comanche that was given to me for free about 4 years ago. The truck ran, but had a lot of little things wrong that the owners couldn't fix themselves and didn't want to pay someone to do it. So the price was right and I like the truck so... I use the truck mostly for utility, hauling brush, compost and firewood. I drive the truck in winter when I can't ride my motorcycles to work. I put about 1000 miles a year on the beast. So for my questions. I just sprung a leak in the rear brake line. It is in the hard line behind the gas tank. I have never had to replace solid brake line before, but it looks straight forward. What diameter is the brake line and can I splice into the line or should I replace to whole thing? Any advice would be great. Also, I am going to intall a heater for the winter this year. Anyone have any recomendations? I was thinking towards a tank heater since I have to change the coolant before winter. Thanks, Joe